Dowel support for concrete pavement expansion joints



C. A. LORD DOWEL SUPPORT FOR CONCRETE PAVEMENT EXPANSION JOINTS FiledDec. 21, 1936 Patented Oct. 18, 1938 UNITED STATES PATENT OFFICE DOWELSUPPORT FOR CONCRETE PAVE DIENTEXPANSION JOINTS tion of IllinoisApplication December 21, 1936, Serial No. l16,898

6 Claims- This invention relates to the art of concrete pavementexpansion joints of the known type wherein the meeting ends of thepavement at the joint have embedded therein dowels extending across thejoint and usually coated with grease on one side of the joint to permitrelative slip as the concrete expands or contracts under temperaturechanges. In the use of such dowels it is essential to the properfunctioning that they be located accurately parallel to the axis of thepavement.

It has been the practice heretofore to rest the end portions of thedowel bars on supports known as chairs, either directly, or on crossrods extending between and seated on the chairs of each row on each sideof the joint. The chairs include a pointed leg or legs that are driveninto the dirt bed or floor on which the concrete is spread, and if, asoften happens, the chairs of a row are not set to the same depth or oneor more of them accidentally gets depressed too far into the bed or videan improved chair structure by which the leg or legs of the latter canpenetrate the bed only to a predetermined distance. Another object hasbeen to provide an improved structure of dowel bar support by which theseveral chairs of each row are tied to each other in fixed spacedrelation and so that adjacent chairs in the same row cannot tilt towardor from each other. Still another object has been to provide an improveddowel bar support wherein the two rows of chairs are maintained paralleland at fixed distances from each other and from the pavement joint.

Other objects and advantages of the invention will be apparent topersons skilled in the art from the following detailed description,taken in connectionwith the accompanying drawing wherein I haveillustrated preferred embodiments of the invention, and in which- Fig. 1is a perspective view of the preferred Fig. 4 is a fragmentary section,crosswise of the the form of chair shown in Figs. 1 and 2, said.

chair is preferably a one-piece structure consisting of a singlelength'of heavy wire bent to form a pair of downwardly divergent legs I,a lateral support II for a dowel bar laid between the limbs thereof,said limbs being continuous with the upper ends of the legs Ill, and a.seat 12 formed by contiguous twin limbs for a cross bar extendingbetween adjacent chairs of a. single row and itself forming a directsupport for the dowel bar.

The lower ends of the legs III are, of course, de-' signed to beimpressed into the dirt bed on which the pavement is laid.

As shown in Fig. 2, round cross bars or rods ii are laid in the seats I!of the chairs of each row, and the dowel bars ll, which extend acrossthe joint are directly supported adjacent to their ends on the, crossbars i3 and extend through the lateral dowel bar supports H. P and P(Fig. 4) designate the end portions of the pavement sections on the twosides of the joint, and S designates the usual flat slab of asphalt orlike material that is commonly inserted as a packing between the meetingends of the concrete sections. This slab is formed with transverse holesl5 .through which the dowel bars ll extend.

In prior constructions with which I am acquainted, the chairs of eachrow, whatever their structure, have been independent units, entirelyunconnected except for the cross bars I3 occupying the seats of thechairs. As hereinbefore stated, unless the chair seats of the two rowsare kept at substantially the same level, obviously the'dowel bars Itwill not be in perfect parallel-' ism which is essential to a goodexpansion joint of this character. To obviate this fault, I provide inassociation with each row of chairs a rod it which extends lengthwise ofthe row and is secured, preferably by spot or tack welding to the legsof the chairs a slight distance above the lower ends of the legs. Thisrod li serves two useful functions. In the first place, it limits thedepth of penetration of the chair legs into the pavementbed, so that allof the chairs will be impressed to the same .extentinto the bed, thusmaintaining their seats. l2ona common level;

and in the second place, it rigidlyconnects and spaces the severalchairs of each row so that the cannot tilt toward or from each other.

the joint and each other.

The two dowel bar supporting structures are preferably located atequal-or substantially equal distances from the joint and in parallelismwith To insure this accurate disposition of the, two rows of supports, Iemploy means for rigidly connecting them across the joint. The meanspreferably used and herein illustrated consists of cross rods I],extending across the joint and disposed at spaced intervals lengthwiseof the two supporting structures, the ends of said rods II being securedas by spot or tack welding to the rods 16. Preferably, and as hereinshown, each rod H is formed substantially midlength thereof, with adownward U- shaped offset l8,'which seats and embraces the lower edgeportion of the packing slab S.

In Fig. 5 I have illustrated a slightly modified form of the one-piecechair, wherein the seat II for the cross bar It, instead of being formedas a continuation of the lateral dowel bar support Ii, is formed as alateral offset of one of the legs I0. While the form of chairillustrated in Figs. 1 .and 2 is preferred, the form shown in Fig. 5 maybe substituted therefor to practically the same effect if desired.

By virtue of the described construction, the dowel bars I can never getout of true parallelism either when erecting the chairs or when pouringthe concrete; and by rigidly connecting the chairs .of each row and alsothe pairs of rows, the entire joint reinforcing structure retains itsform and correct position when'and after the concrete is spread.

While I have illustrated and described a preferred embodiment of theinvention, it is manifest that many of the structural details may bevaried without departing from the operative principle of the invention,and hence I do not.

limit the latter to the specific form shown, but reserve all suchvariations, modifications and 'mechanical equivalents as fall within thespirit and purview of the claims.

I claim:

1. A two-legged dowel bar supporting chair for concrete pavementextension joints, consisting of a single length of wire bent to form apair of legs consisting of end portions of the wire disposed in a commonplane, a lateral sup;-

port for a dowel bar located between and in the plane of said legs, anda cross bar seat latrods extending across and secured to the lowererally ofiset from-the plane of said legs and lateral support. Atwo-legged dowel bar supporting chair for concrete pavement expansionjoints, con-.

sisting of a single length of wire bent to form a pair of legsconsisting of end portions of the wire disposed in a common plane, alateral support for a dowel bar located between and in the plane of saidlegs, and a cross bar seat .2,188,558 1 I I g formed by contiguous twinU-shaped limbs, continuous with said lateral support and laterallyofi'set. from the plane of said legs and lateral support.

3. A two-legged dowel bar supporting chair for concrete pavementexpansion joints, consisting of a single length of wire bent to form apair of legs consisting of end portions of the wire, a lateral supportfor'a dowel bar continuous with the upper ends of said legs and lyingbetween and in the plane of the latter, and a cross bar seat formed by alaterally oifset portion of one leg located between the upper and lowerends of the latter.

4- In a continuous spacer and support for dowel bar assemblies forconcrete pavement expansion joints, the combination with parallel rowsof 'chairs disposed respectively on opposite 1 sides of the joint, eachchair having a leg formed with a free lower end adapted to be driveninto the dirt bed of the pavement and the legs of all the chairs in eachrow being located in a common plane transverse to the roadway, of rodsextending across and secured to the lower portions of ,the legs of thechairs of the two rows respectively, and means connected to said rodsextending across the joint and rigidly connecting and spacing said rows.

'5. In a continuous spacer and. support for .two rows respectively, androds connecting and spacing said first-named rods across the joint.

6. In a continuous spacer and support for dowel bar assemblies forconcrete pavement expansion joints,- the combination with parallel rowsof chairs disposed respectively on opposite sides of the joint, eachchair having a pair of legs formed with free lower ends adapted to bedriven into the dirt bed of the pavement and the. legs of all the chairsof each row being locatedin a common plane transverse to the roadway, of

portions of the legs of the chairs of the two rows respectively, androds connecting and' spacing said first-named rods across the joint,said last named rods formed with downwardly oifset' portions adapted toseat and embrace the lower edge portion of a joint packing slab.

' CHESTER A. LORD.

